This invention relates to delivering biologically active compounds to cells.
In various situations it is desirable to deliver a biologically active compound through the cell membrane to inner cell structures. For example, drugs or cytotoxins may have little effect if trapped in the medium outside the cell membrane but may be extremely potent once inside the cell.
It is also desirable to deliver such biologically active compounds to selected cells in a heterogeneous cell population. For example, in treating diseased or infected cells such as virus-infected cells or transformed or malignant cells, it is desirable to deliver cytotoxins to the diseased or malignant cells but not to normal cells. One approach disclosed for targeting malignant cells uses an antibody-toxin conjugate. The antibody is specific for malignant cells and delivers the toxin to them. To be effective, such systems should deliver the toxin with high selectivity to the target cells, without unnecessarily reducing the effectiveness of the active substance. These problems are particularly important where the goal is destruction of infected or diseased cells in vivo without harming normal cells.
Ritz et al. (1980) Nature 283:583-585 disclose monoclonal antibody (J5) that is specific for common acute lymphoblastic leukemia antigen.
Barbieri et al. (1982) Biochem J. 203:55-59 disclose purification and partial characterization of an antiviral protein known as pokeweed antiviral protein-S ("PAP-S").
Ramakrishnan et al. (1984) Cancer Research 44:1398-1404 disclose conjugating PAP proteins to anti-Thy 1.1, a monoclonal antibody. The conjugate is used to inhibit protein synthesis selectively in Thy 1.1-positive target leukemia cells. The linker used to form the conjugate is N-succinimidyl-3-(2-pyridyldithio) propionate. When the disulfide bond is cleaved, the free PAP toxin is produced.
Neville et al. U.S. Pat. No. 4,359,457 disclose a conjugate of anti-Thy 1.2 monoclonal antibody and ricin used as a tumor suppressive composition against lymphoma. The linking agent used is m-maleimidobenzoyl-N-hydroxysuccinimide.
The above approaches either depend on the toxicity of an antibody-toxin conjugate, or they depend on disulfide bond cleavage, a phenomenon that may be difficult to control temporally and spatially to avoid release of the toxin before delivery to the targeted cells.
Rich et al. (1975) J. Am. Chem. Soc. 97:1575-9 disclose a 3-nitro-bromomethylbenzoylamide polystyrene resin to immobilize amino acids for solid-phase peptide synthesis. The synthesized peptide is detached from the resin by photolysis.
Patchornik et al. (1970) J. Am. Chem. Soc. 92:6333-6335 disclose the use of o-nitrobenzyl derivatives for protecting the amino function of peptides. The protecting group is removed by irradiation with light of wavelengths longer than 3200 Angstroms. Specific blocking groups disclosed are 6-nitroveratryloxy-carbonyl (NVOC) and 2-nitrobenzyloxycarbonyl (NBOC) groups. 2,2'-Dinitrodiphenylmethanol is disclosed as a blocking group for the carboxylic terminal function of a peptide chain.
Kaplan et al. (1978) Biochemistry 17:1929-1935 disclose inactivated ("caged") adenosine 5'-triphosphate (ATP) that is covalently attached to 2-nitrobenzyl and 1-(2-nitro) phenethyl groups. The caged ATP is exposed to light to release ATP upon demand.
Nargeat et al. (1980) PNAS (USA) 80:2395-2399 disclose U.V. irradiation of o-nitrobenzyl esters of cAMP and cGMP to generate cAMP and cGMP in a biological system.